Earlier this year I wrote about some ruler art I used to draw in middle school, which looked like this:
The pleasing thing to me in middle school was that a series of straight lines could produce a curved boundary. Here it is, highlighted in red:
It turns out that this curve is a quadratic Bézier curve. In fact, the red line on the above image is just an SVG path of a quadratic Bézier curve, using the basis lines' endpoints as the Bézier control points. The path has a d value equivalent to M 0,0 Q 0,1, 1,1.
Here are a few other drawings from the earlier post, highlighting their curves the same way: